1. Field of Invention
The invention relates to a fan with multiple impellers coupled in series and a fan frame thereof. In particularly, the invention relates to a fan with dual impellers coupled in series, which has a single fan frame, and a fan frame thereof.
2. Related Art
The electronic products have been rapidly developed towards more compact and higher performance, frequency and operation speed, which accompany the increased heat. The increased heat causes the unstable issue of the electronic products and further affects the reliability and lifetime of the electronic products. Thus, the heat dissipation issue has become one of the important subjects of the electronic products. Fans are frequently used heat dissipating devices in the electronic products. Moreover, in order to enhance the heat dissipating efficiency, several fans are connected in series to form a fan with multiple impellers so as to increase the air quantity and pressure of the airflow.
As shown in FIG. 1, a conventional fan 1 includes a front impeller 11, a front fan frame 12, a rear impeller 13 and a rear fan frame 14. The front impeller 11 is disposed in the front fan frame 12 and telescoped to a bushing 121 of the front fan frame 12. The rear impeller 13 is disposed in the rear fan frame 14 and telescoped to a bushing 141 of the rear fan frame 14. The front and rear impellers 11, 13 are connected in series. In addition, the fan 1 has a fixing element 15, such as a tenon, a screw or a rivet, to fasten the front fan frame 12 and the rear fan frame 14. Accordingly, when the front and rear impellers 11, 13 are operated simultaneously, the fan 1 can generate the airflow with increased air quantity and pressure so as to enhance the heat dissipating efficiency.
However, after the fan 1 rotates under a high speed for a long period, the fixing element 15 may be unstable due to the torque of the rotating impellers. The unstable fixing element 15 will cause the vibrations, which may damage the sensitive components of the electronic products. Moreover, if the fixing element 15 is loosened, the front and rear fan frames 12, 14 will separate from each other. This will lead to the malfunction of the fan 1, and further cause the shut down or break down of the electronic product because the heat can not be dissipated in time.
Again referring to FIG. 1, since the fan 1 is composed of two fan frames 12 and 14, the ribs 122 and 142 must be longer or thicker to provide sufficient structural strength. Thus, the frame thickness D of the fan 1 is larger, so that the size of the fan 1 increases. Therefore, the usable space of the electronic product with the fan 1 is decreased, so the product competitiveness thereof may be lower.
Therefore, it is an important subject to provide a fan with multiple impellers and fan frame thereof that can prevent the problems of unstable connection and loosening, increase the structural strength, reduce the cost of material and assembling, decrease the size and enhance the product performance.